Determining the occurrence of a 3(10)-helix and an alpha-helix in two different segments of a lipopeptaibol antibiotic using TOAC, a nitroxide spin-labeled C(alpha)-tetrasubstituted alpha-aminoacid.

Trichogin GA IV is a 11-residue lipopeptaibol antibiotic exhibiting membrane modifying properties. We synthesized step-by-step by solution methods three trichogin analogues, each with a double Aib (alpha-aminoisobutyric acid)-->TOAC (2,2,6,6-tetramethylpiperidine-1-oxyl-4-amino-4-carboxylic acid) replacement. The strict similarity in the conformational propensities of Aib and TOAC allowed us to exploit these analogues in a detailed investigation of the conformation of this lipopeptaibol in different organic solvents and in a membrane-mimetic environment using in particular the double spin labeling ESR technique. We conclude that the secondary structure in solution remains essentially unchanged if compared to that previously found in the crystal state for trichogin. More specifically, the N-terminal region of the peptide folds in a 3(10)-helix, while the central and C-terminal regions are mainly alpha-helical. An additional, significant proof for the modest plasticity of the trichogin structure was obtained by an X-ray diffraction analysis of the nOct-[TOAC4,8, Leu-OMe11] analogue. For the three analogues permeability measurements revealed membrane-modifying properties comparable to those of natural trichogin.

[1]  C. Toniolo,et al.  Effect of Nα-Acyl Chain Length on the Membrane-Modifying Properties of Synthetic Analogs of the Lipopeptaibol Trichogin GA IV , 1996 .

[2]  M. Sansom.  The biophysics of peptide models of ion channels. , 1991, Progress in biophysics and molecular biology.

[3]  C. Toniolo,et al.  Peptaibol antibiotics: a study on the helical structure of the 2-9 sequence of emerimicins III and IV. , 1982, Proceedings of the National Academy of Sciences of the United States of America.

[4]  J. Kendrew,et al.  Polypeptide chain configurations in crystalline proteins , 1950, Proceedings of the Royal Society of London. Series A. Mathematical and Physical Sciences.

[5]  I. Karle,et al.  Structural characteristics of alpha-helical peptide molecules containing Aib residues. , 1990, Biochemistry.

[6]  C. Toniolo,et al.  Linear oligopeptides, 29. Infrared conformational analysis of homo‐oligopeptides in the solid state and in solution , 1976 .

[7]  S. Rebuffat,et al.  Trichogin A IV, an 11-residue lipopeptaibol from Trichoderma longibrachiatum , 1992 .

[8]  R Miller,et al.  Structure solution by minimal-function phase refinement and Fourier filtering. II. Implementation and applications. , 1994, Acta crystallographica. Section A, Foundations of crystallography.

[9]  C. Toniolo,et al.  Distinguishing helix conformations in alanine-rich peptides using the unnatural amino acid TOAC and electron spin resonance , 1996 .

[10]  C. Ramakrishnan,et al.  Study of hydrogen bonds in amino acids and peptides. , 2009, International journal of protein research.

[11]  C. Corvaja,et al.  Synthesis and conformational studies of peptides containing TOAC, a spin‐labelled Cα,α‐disubstituted glycine , 1995 .

[12]  C. Toniolo,et al.  Solution conformational analysis of amphiphilic helical, synthetic analogs of the lipopeptaibol trichogin GA IV. , 2009, The journal of peptide research : official journal of the American Peptide Society.

[13]  H. Lemaire,et al.  Le téréphthalate de di(tétraméthyl-2,2,6,6 pipéridinyl-4 oxyle-1) est-il un biradical à échange fort ou à échange faible? , 1968 .

[14]  G. Fasman.  Macromolecules. (Book Reviews: Poly-alpha -Amino Acids. Protein Models for Conformational Studies) , 1967 .

[15]  C. Toniolo,et al.  Studies of peptides forming 3(10)- and alpha-helices and beta-bend ribbon structures in organic solution and in model biomembranes by Fourier transform infrared spectroscopy. , 1991, Biochemistry.

[16]  K. Chou.  Prediction and classification of α‐turn types , 1997 .

[17]  C. Toniolo,et al.  Structure determination of racemic trichogin A IV using centrosymmetric crystals , 1994, Nature Structural Biology.

[18]  H. Scheraga,et al.  Statistical and energetic analysis of side-chain conformations in oligopeptides. , 2009, International journal of peptide and protein research.

[19]  A. Lombardi,et al.  Discovering protein secondary structures: Classification and description of isolated α‐turns , 1996 .

[20]  G. R. Luckhurst.  Alternating linewidths. A novel relaxation process in the electron resonance of biradicals , 1966 .

[21]  G. Rose,et al.  Turns in peptides and proteins. , 1985, Advances in protein chemistry.

[22]  D. Cremer,et al.  General definition of ring puckering coordinates , 1975 .

[23]  C. Venkatachalam.  Stereochemical criteria for polypeptides and proteins. V. Conformation of a system of three linked peptide units , 1968, Biopolymers.

[24]  M. Huggins.  The Structure of Fibrous Proteins. , 1943 .

[25]  L. A. Carpino.  1-Hydroxy-7-azabenzotriazole. An efficient peptide coupling additive , 1993 .

[26]  C. Toniolo,et al.  ESR Characterization of Hexameric, Helical Peptides Using Double TOAC Spin Labeling , 1996 .

[27]  L. J. Bellamy.  The infra-red spectra of complex molecules , 1962 .

[28]  H. Scheraga,et al.  Conformational analysis of the 20 naturally occurring amino acid residues using ECEPP. , 1977, Macromolecules.

[29]  Olga Kennard,et al.  The geometry of the N–H⋯O=C hydrogen bond. 3. Hydrogen-bond distances and angles , 1984 .

[30]  Steven M. Gallo,et al.  SnB: crystal structure determination via shake-and-bake , 1994 .

[31]  I. C. O. B. Nomenclature.  IUPAC-IUB Commission on Biochemical Nomenclature. Abbreviations and symbols for the description of the conformation of polypeptide chains. Tentative rules (1969). , 1970, Biochemistry.

[32]  M. Tsuboi,et al.  Additional Studies on the Intramolecular Hydrogen Bonding in Acetylglycine N-Methylamide , 1952 .

[33]  W. König,et al.  Eine neue Methode zur Synthese von Peptiden: Aktivierung der Carboxylgruppe mit Dicyclohexylcarbodiimid unter Zusatz von 1‐Hydroxy‐benzotriazolen , 1970 .

[34]  S. Rebuffat,et al.  Interaction of trichorzianines A and B with model membranes and with the amoeba Dictyostelium. , 1989, Biochimica et biophysica acta.

[35]  Olga Kennard,et al.  Hydrogen-bond geometry in organic crystals , 1984 .

[36]  Olga Kennard,et al.  Geometry of the nitrogen-hydrogen...oxygen-carbon (N-H...O:C) hydrogen bond. 2. Three-center (bifurcated) and four-center (trifurcated) bonds , 1984 .

[37]  G. Millhauser,et al.  Increasing sequence length favors alpha-helix over 3(10)-helix in alanine-based peptides: evidence for a length-dependent structural transition. , 1993, Biochemistry.

[38]  G. R. Luckhurst.  4 – Biradicals as Spin Probes , 1976 .

[39]  C. Toniolo,et al.  Structures of polypeptides from α-amino acids disubstituted at the α-carbon , 1991 .

[40]  C. Toniolo,et al.  The polypeptide 310-helix. , 1991, Trends in biochemical sciences.

[41]  C. Görbitz,et al.  Hydrogen-bond distances and angles in the structures of amino acids and peptides , 1989 .

[42]  C. Nakaie,et al.  A NOVEL SPIN-LABELED AMINO-ACID DERIVATIVE FOR USE IN PEPTIDE-SYNTHESIS - (9-FLUORENYLMETHYLOXYCARBONYL)-2,2,6,6-TETRAMETHYLPIPERIDINE-N-OXYL-4-AMINO-4-CARBOXYLIC ACID , 1993 .

[43]  G. Millhauser,et al.  Short alanine-based peptides may form 310-helices and not α-helices in aqueous solution , 1992, Nature.

[44]  C. Toniolo,et al.  TOAC, a nitroxide spin‐labeled, achiral Cα‐tetrasubstituted α‐amino acid, is an excellent tool in material science and biochemistry , 1998 .

[45]  M. Bally,et al.  Production of large unilamellar vesicles by a rapid extrusion procedure: characterization of size distribution, trapped volume and ability to maintain a membrane potential. , 1985, Biochimica et biophysica acta.

[46]  P. Piotrowiak,et al.  Spin and Reaction Dynamics in Flexible Polymethylene Biradicals As Studied by EPR, NMR, and Optical Spectroscopy and Magnetic Field Effects. Measurements and Mechanisms of Scalar Electron Spin-Spin Coupling , 1992 .

[47]  C. Toniolo,et al.  Intramolecularly hydrogen-bonded peptide conformations. , 1980, CRC critical reviews in biochemistry.